Typically, in modem communications, a tone with 180 degree phase reversal and a period following this transition to allow reliable detection of the reversal, is used to signal the other side the presence of an event, for example, detection of DPSK sequence, beginning of line probing signal, finishing of channel analysis, beginning and ending of round trip delay measurement timer, and so on.
The timing of the transition must be measured precisely to allow the receiver to be set correctly. Some transition detectors that are known in the art utilize complex coherent schemes to give a highest correlation between locally generated tones and the received signal. Other transition detectors utilize trellis techniques based on known subsequences of symbols that preceded and followed a transition. Thus, there is a need for a non-complex phase reversal detector and method that simplifies transition detection.